Television receiver



Aug. 5, 1958 E. JONES ETAL 2,846,606

TELEVISION RECEIVER Filed June 10, 1953 IN VENTOR6 In: Zyn done-s J'fenhe 2h Edward Marita AGENT 2,846,605 Patented Aug. 5, 1958 Zfiddfifld ELEVlSiGl l Emlyn Jones, Hurley, and Kenneth Edward Martin, Rochampton, London, England, t more, by mesne assignments, to Nat-tilt American Philips flcmpany, ind, New York, N. "ad, a corporation as? Application dune ill, 1953, Serial Ne. 2:38, "72 2 (Claims. (Cl. 291?)76) is to say, the line coils are arranged substantially at right angles to the frame coils which is necessary for the purpose of producing a rectilinear raster and ensuring that cross talk between line and frame coils is at a minimum.

Even when this precaution has been taken it has been noticed that with certain designs of line and frame coil assembly an undesirable effect similar to that produced by cross talk has made its appearance, this being in the form of a displacement of the scanning spot in an oscillating manner normal to the line direction so giving rise to what may be termed a rippling of the scanning lines extending over a portion of the lines from their commencement.

The object of the present invention is to provide simple and eflicient means for substantially reducing or preventing this undesirable effect.

It has previously been considered that this effect is due to residual cross talk between the frame and line coils which could not be entirely neutralized by normal methods, but we have now discovered that this is not the case. During investigation of this rippling effect it was discovered that it was present even when the frame coils were removed from the deflecting coil assembly, and further investigation showed that the alternating magnetic deflecting field giving rise to the rippling of the lines was due to unbalance between the currents in the two sections of the line deflection winding at a frequency considerably higher than the line scanning frequency.

According to the present invention therefore a line and frame deflecting coil assembly for a television receiver is characterized by the provision of means associated with the line deflecting coils substantially to cancel or neutralize any alternating component of the fields produced by the coils which is at right angles to the axis of the coils and which has a frequency many times the line scanning frequency.

Further features of the invention will be apparent from the following description of one embodiment which is given by way of example only with reference to the drawing in which:

Figure 1 shows an end elevation of a deflecting coil assembly having a slotted yoke of magnetizable material and Figure 2 shows a section on the line A-A' of Figure 1.

Referring now to the drawings which show a line and frame deflecting coil assembly of the usual type, the line deflecting winding comprises two coil sections indicated at 1 and 2, and the frame deflecting coils at 3 and 4 (Figure 1), the substantially parallel portions of the coil sections 1, 2 being housed in slots in a yoke 5 which may be of ferromagnetic cubic ferrite material.

The slotted yoke 5 displays projecting pole pieces 7 and 8 which project between the two sections of the line Winding. As explained above, during operation and due to a lack of electrical symmetry between the two halves of the line coil a stray alternating field having a frequency many times the line frequency and having a component at right angles to the axis of the coils may be produced thus producing the undesired rippling effect.

In order substantially to neutralize or cancel this component an auxiliary winding 9, 10 is provided on one or each of the pole pieces 7 and 8. This winding may comprise a single short circuited turn or a number of short circuited turns. The number of turns and the resistance thereof is chosen such that at the ripple frequency the desired cancellation or neutralization is achieved.

In a modification the auxiliary winding or windings instead of being short circuited is or are electrically connected through a capacitor or capacitors and if desired the value of this capacitor or capacitors may be chosen so that together with the inductance of the associated winding a circuit resonance at the ripple frequency is produced.

it will be understood that the invention is not limited to the above described embodiment since changes may be made to suit particular circumstances as they arise in practice.

What is claimed is:

l. A television deflection coil assembly, comprising a pair of line deflection coils positioned to face each other thereby to produce a magnetic line deflection field therebetween when energized, a pair of frame deflection coils positioned to face each other thereby to produce a magnetic frame deflection field therebetween when energized, said pairs of line and frame coils being oriented with respect to each other so that said line and frame deflection fields mutually intersect at right angles, said line deflection coils having the property of producing an undesired alternating magnetic field at a right angle with respect to said line deflection field, said undesired magnetic field having a higher frequency of alternation than does said frame deflection field, and compensating means comprising an electrical coil positioned on a line extending between said line deflection coils and in the path of said undesired magnetic field, said coil being oriented with its axis parallel to the flux lines of said undesired magnetic field so as to be magnetically coupled to said undesired magnetic field without being coupled to said line deflection field, whereby the effective magnitude of said undesired magnetic field is reduced without affecting said line deflection field.

2. A deflection coil assembly as claimed in claim 1, including a hollow yoke of magnetic material positioned to substantially surround the assembly of deflection coils, said yoke having at least one pole piece extending inwardly through one of said frame coils between said line deflection coils, said electrical coil being positioned on and surrounding said pole piece.

References Cited in the file of this patent UNITED STATES PATENTS 2,155,514 Tolson et al. Apr. 25, 1939 2,228,821 Hansen Jan. 14, 1941 2,543,720 Hoyt Feb. 27, 1951 2,561,586 Montgomery July 24, 1951 2,569,343 Skull Aug. 10, 1949 2,598,303 Reinhard May 25, 1952 FOREIGN PATENTS 627,482 Great rit in WWWWM Aug. .10, 9%?! 

